U.S. patent application number 16/461141 was filed with the patent office on 2019-09-12 for optimized electrical machine.
The applicant listed for this patent is Robert Bosch GmbH. Invention is credited to Mickael Kremer, Johannes Riedl, Sebastian Tabarelli.
Application Number | 20190280539 16/461141 |
Document ID | / |
Family ID | 59923412 |
Filed Date | 2019-09-12 |
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United States Patent
Application |
20190280539 |
Kind Code |
A1 |
Kremer; Mickael ; et
al. |
September 12, 2019 |
OPTIMIZED ELECTRICAL MACHINE
Abstract
An electrical machine (10) for driving a vehicle comprises: a
stator (14) having stator grooves (34) running axially and running
uniformly around an axis of the electrical machine (10), through
which grooves a stator winding (42) runs; and a rotor (12) with
axially running poles (16), which rotor is mounted inside the
stator (14) for rotation around the axis of the electrical machine
(10), wherein two pole magnets (20) with rectangular cross-section
are arranged in each pole (16) of the rotor (12) in an axially
running pole opening (18) forming a V in respect of one another.
The electrical machine (10) is optimized with respect to a
plurality of geometrical parameters which have been optimized by
optimization of optimization parameters which are determined from
the geometric parameters.
Inventors: |
Kremer; Mickael; (Hemmingen,
DE) ; Tabarelli; Sebastian; (Herrenberg, DE) ;
Riedl; Johannes; (Muenchen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Robert Bosch GmbH |
Stuttgart |
|
DE |
|
|
Family ID: |
59923412 |
Appl. No.: |
16/461141 |
Filed: |
September 13, 2017 |
PCT Filed: |
September 13, 2017 |
PCT NO: |
PCT/EP2017/073000 |
371 Date: |
May 15, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02K 2201/06 20130101;
H02K 1/2766 20130101; H02K 29/03 20130101; H02K 2213/03 20130101;
H02K 1/276 20130101; H02K 21/16 20130101 |
International
Class: |
H02K 1/27 20060101
H02K001/27; H02K 21/16 20060101 H02K021/16 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2016 |
DE |
10 2016 222 398.4 |
Claims
1. An electrical machine (10) for driving a vehicle, the electrical
machine comprising: a stator (14) having stator grooves (34)
running axially, and running uniformly around an axis of the
electrical machine (10), through which grooves a stator winding
(42) runs; and a rotor (12) with axially oriented poles (16),
wherein the rotor is mounted inside the stator (14) for rotation
about the axis of the electrical machine (10), wherein two pole
magnets (20) of rectangular cross-section are arranged in each pole
(16) of the rotor (12) in an axially oriented pole opening (18),
forming a V in respect of one another, wherein a geometrical
angular offset (wM) of the two pole magnets (20), by which the two
pole magnets (20) are offset in a V-shaped arrangement in relation
to one another, is less than 15.degree.; wherein an electrical
angle of an outer pole coverage (wA) lies between 115.7.degree. el
and 133.2.degree. el; wherein an electrical angle of an inner pole
coverage (wI) lies between 123.5.degree. el and 142.9.degree. el;
wherein an electrical angle is determined as a geometrical angle
multiplied by one half of a number of poles (16) of the rotor (12);
wherein the outer pole coverage (wA) is determined by an axial
geometrical angle by which the two pole magnets (20) cover on a
radially outer side of the pole opening (18); and wherein the inner
pole coverage (wI) is determined by an axial geometrical angle
which the two pole magnets (20) cover on a radially inner side of
the pole opening (18).
2. The electrical machine (10) as claimed in claim 1, wherein the
stator (14): has a ratio of a tooth height (hz) to a yoke thickness
(hj) between 0.959 and 1.126; has a ratio of a tooth width (bZA) to
a groove width (bNA) at a tooth gullet (38) between 1.23 and 1.35;
has a ratio of a tooth width (bZI) to a groove width (bNI) at a
tooth tip (40) between 1.03 and 1.14; and has a ratio of the groove
width (bNA) at the tooth gullet (38) to the groove width (bNI) at
the tooth tip (40) between 0.9 and 1.1.
3. The electrical machine (10) as claimed in claim 1, wherein the
stator (14): has a ratio of the tooth height (hz) to the yoke
thickness (hj) between 1.395 and 1.6376; has a ratio of the tooth
width (bZA) to the groove width (bNA) at the tooth gullet (38)
between 1.33 and 1.47; has a ratio of the tooth width (bZI) to the
groove width (bNI) at the tooth tip (40) between 1.06 and 1.19; and
has a ratio of the groove width (bNA) at the tooth gullet (38) to
the groove width (bNI) at the tooth tip (40) between 0.9 and
1.1.
4. The electrical machine (10) as claimed in claim 1, wherein an
external diameter of the stator (dSA) lies between 110 and 500
mm.
5. The electrical machine (10) as claimed in claim 1, wherein the
electrical machine (10) has a slot number greater than or equal to
1.
6. The electrical machine (10) as claimed in claim 1, wherein a
ratio of an internal diameter (dSI) to an external diameter (dSA)
of the stator (14) lies between 0.75 and 0.85.
7. The electrical machine (10) as claimed in claim 1, wherein a
ratio between a width (d) of an air gap (26) between the stator
(14) and the rotor (12) and an internal diameter (dSI) of the
stator (14) lies between 0.0025 and 0.0055.
8. The electrical machine (10) as claimed in claim 1, wherein a
clearance (m) between two pole magnets (20) in a pole (16), in a
circumferential direction, is less than 3.0 mm.
9. The electrical machine (10) as claimed in claim 1, wherein the
pole opening (18) is V-shaped, and has no central web.
10. The electrical machine (10) as claimed in claim 1, wherein a
ratio of a radial thickness (hSA) of the web (28) between the pole
opening (18) and an outer circumference of the rotor (12), at an
circumferential edge, to a thickness (hSI) of the web (28) at a
point of initial contact between a pole magnet (20) and the web
(28), lies between 0.7 and 1.2.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to an electrical machine, such as an
electric motor or a generator.
[0002] The use of permanent magnet excited synchronous machines in
non-chargeable and chargeable hybrid vehicles is widespread. In the
case of synchronous machines which are integrated in a combustion
engine, rotors are frequently employed having two magnets in a
v-shaped arrangement per pole.
[0003] The optimization of electrical machines of this type
involves conflicting optimization objectives. For traction drive
systems in the electromobility sector, high torque or power
densities are required. At the same time, it is necessary for
costs, structural space, losses, torque ripple and noise to be
minimized.
[0004] DE 10 2012 219 174 A1 indicates that, for example, for an
electrical machine having a slot number q=2, torque ripple can be
minimized if the magnetic aperture angle lies between 76.2% and
81.6%.
[0005] EP 2 498 375 A1 describes an electrical machine having a
pole coverage factor between 0.45 and 0.55.
[0006] WO 2006 095 887 A1 describes an electrical machine with a
rotor, having pole openings with a central web, and wherein the
pole coverage factor lies between 127.degree. el and 140.degree.
el.
[0007] It is further known, in synchronous machines which are
integrated in a combustion engine, for a stator with a single-tooth
winding to be employed, said winding having a slot number q=0.5.
This type of winding generally minimizes the length of the winding
overhang, and permits the configuration of synchronous machines
with a short axial length. At q=0.5, however, the electromagnetic
field in the air gap between the rotor and the stator contains a
high proportion of harmonics. This results in increased rotor
losses and an increase in the temperature of the magnets. For
longer machines which are integrated in a combustion engine, an
integer-slot winding, for example having a slot number q=2 can be
employed, thereby resulting in an electromagnetic field in the air
gap containing a lower proportion of harmonics. Reduced eddy
current losses will then occur in the magnets, as a result of
which, in turn, the temperature of the magnets remains lower, thus
permitting the use of magnets with a more cost-effective class
rating.
SUMMARY OF THE INVENTION
[0008] In order to achieve the above-mentioned optimization
objectives, multi-objective optimization can be employed. To this
end, a large number of design variants are calculated, and the best
combinations of geometrical parameters for the electrical machine
can be identified.
[0009] Forms of embodiment of the present invention can
advantageously permit the provision of electrical machines in which
a plurality of properties, including losses, construction costs,
efficiency, torque ripple and noise, are optimized in relation to
one another.
[0010] Concepts for forms of embodiment of the present invention
can, inter alia, be considered to be based upon the principles and
findings described hereinafter.
[0011] The invention relates to an electrical machine for driving a
vehicle, including, for example, a private car, an HGV, a bus,
etc., in particular a non-chargeable and chargeable hybrid vehicle.
The electrical machine can be a permanent magnet excited
synchronous machine and/or can be a synchronous machine which is
integrated in a combustion engine. For example, the rotor of the
electrical machine can be mounted directly on the drive shaft of a
combustion engine.
[0012] According to one form of embodiment of the invention, the
electrical machine comprises a stator having stator grooves running
axially, and running uniformly around an axis of the electrical
machine, through which grooves a stator winding runs, and a rotor
with axially oriented poles, which rotor is mounted inside the
stator for rotation about the axis of the electrical machine,
wherein two pole magnets of rectangular cross-section are arranged
in each pole of the rotor in an axially oriented pole opening,
forming a V in respect of one another.
[0013] In multi-objective optimization, it has been established
that the following geometrical parameters and/or structural
variables of the rotor and/or of the stator of an electrical
machine of this type result in the optimization of a large number
of optimization objectives or optimization parameters, including
the achievement of a desired torque or a desired speed of rotation
requirement, a maximization of efficiency, a minimization of noise,
a minimization of costs, a minimization of torque ripple and a
minimization of any short-circuit current or short-circuit
losses.
[0014] The electrical machine is optimized with respect to a
plurality of geometrical parameters, which have been optimized by
the optimization of optimization parameters or optimization
objectives, which are dictated by said geometrical parameters.
[0015] According to one form of embodiment of the invention, in the
rotor: the geometrical angular offset of the two pole magnets, by
which the two pole magnets are offset in a V-shaped arrangement in
relation to one another, is less than 15.degree.; the electrical
angle of the outer pole coverage lies between 115.7.degree. el and
133.2.degree. el; and the electrical angle of the inner pole
coverage lies between 123.5.degree. el and 142.9.degree. el.
[0016] The geometrical angular offset of the two pole magnets can
thus be considered as an angle through which the two magnets are
rotated in relation to one another such that, in combination, they
constitute a V-shape.
[0017] An electrical angle can be determined as a geometrical angle
multiplied by two times the number of poles of the rotor.
[0018] The outer pole coverage can be determined by an axial
geometrical angle which the two pole magnets cover on a radially
outer side of the pole opening. For example, the outer pole
coverage can be determined by the geometrical angle between
radially outer edges, that are circumferentially on the outside, of
the pole magnets.
[0019] The inner pole coverage can be determined by an axial
geometrical angle which the two pole magnets cover on a radially
inner side of the pole opening. For example, the inner pole
coverage can be determined by an axial geometrical angle between
radially inner and circumferentially outer edges of the pole
magnets.
[0020] According to one form of embodiment of the invention, the
stator has the following: a ratio of the tooth height to the yoke
thickness between 0.959 and 1.126; a ratio of the tooth width to
the groove width at the tooth gullet between 1.23 and 1.35; a ratio
of the tooth width to the groove width at the tooth tip between
1.03 and 1.14; and a ratio of the groove width at the tooth gullet
to the groove width at the tooth tip between 0.9 and 1.1.
[0021] Both the grooves and the teeth (excluding the tooth tip) can
have a trapezoidal cross-section. The grooves can have a
rectangular cross-section, which can be advantageous in the case of
a plug-winding, as the plugged-in conductors generally have a
rectangular cross-section.
[0022] The tooth height is the radial height or thickness over
which the annular part of the stator extends, which carries teeth
or grooves. The yoke thickness is the residual radial height or
thickness of the annular part of the stator (i.e. of the yoke)
which carries no teeth or grooves. The tooth gullet is located at
the transition between the teeth and the yoke. The tooth tip is the
end of a tooth, which is oriented in the direction of the rotor and
can optionally be configured with a T-shape. The tooth width and
the groove width are defined in the circumferential direction,
wherein the definition of the tooth width excludes the T-shaped
thickening at the tooth tip.
[0023] The stator parameters stated immediately above, in
combination with the above-mentioned parameters, result in a
particularly optimum electrical machine. However, other
combinations of parameters for the stator are possible, as
described below.
[0024] According to one form of embodiment of the invention, the
stator has the following: a ratio of the tooth height to the yoke
thickness between 1.395 and 1.6376; a ratio of the tooth width to
the groove width at the tooth gullet between 1.33 and 1.47; a ratio
of the tooth width to the groove width at the tooth tip between
1.06 and 1.19; and a ratio of the groove width at the tooth gullet
to the groove width at the tooth tip between 0.9 and 1.1.
[0025] According to one form of embodiment of the invention, the
external diameter of the stator lies between 110 and 500 mm. The
external diameter of the stator is measured from the axis of
rotation of the rotor to the outer circumference of the stator or
the yoke thereof.
[0026] According to one form of embodiment of the invention, the
electrical machine has a slot number greater than or equal to 1.
The slot number of an electrical machine can be determined by the
number of grooves in the stator, divided by the number of phases,
and divided by the number of poles of the rotor. For example, an
electrical machine with three phases and six slots per pole has a
slot number of 2.
[0027] Where the slot number is greater than or equal to 1, for
example 2, an integer-slot winding can be employed, which can in
particular be configured as a plug-winding. By means of a
plug-winding, for example, the copper fullness factor can be
increased, in the interests of reducing copper losses, and a better
thermal connection can be achieved between the winding and the
stator. Moreover, in the event of larger component batch sizes,
costs can be reduced.
[0028] According to one form of embodiment of the invention, the
ratio of the internal diameter to the external diameter of the
stator lies between 0.75 and 0.85, for example between 0.80 and
0.85. The internal diameter of the stator is measured from the axis
of rotation of the rotor to the inner circumference of the stator
or the teeth thereof.
[0029] According to one form of embodiment of the invention, the
ratio between a width of the air gap between the stator and the
rotor and the internal diameter of the stator lies between 0.0025
and 0.0055. Between the stator and the rotor, an annular space is
constituted, which is known as the air gap. The width of the air
gap is determined in the radial direction.
[0030] According to one form of embodiment of the invention, the
circumferential clearance between two pole magnets in a pole is
less than 3.0 mm. If the two pole magnets are not mutually
separated by a central web in the pole opening, this clearance can
be even smaller, for example less than 1.5 mm.
[0031] According to one form of embodiment of the invention, the
pole opening is V-shaped and/or has no central web. In other words,
the pole opening of one pole can comprise two individual openings,
which are mutually separated by the central web. Alternatively, the
pole opening can constitute a continuous V-shaped opening.
[0032] A pole opening with no central web can reduce any stray flux
in the rotor, thereby enhancing efficiency or torque. Moreover, the
inductance of the rotor in the circumferential direction can be
reduced, which may result in the maximization of reluctance torque.
Moreover, the demagnetization resistance of the pole magnets can be
improved by the improvement of the working point thereof.
[0033] According to one form of embodiment of the invention, the
ratio of the radial thickness of the web between the pole opening
and an outer circumference of the rotor, at its circumferential
edge, to the thickness of the web at the point of initial contact
between a pole magnet and the web, lies between 0.7 and 1.2. The
web can be considered as the partition between the pole opening and
an outer circumference of the rotor. In the case of a V-shaped pole
opening, this web has a varying thickness in the radial direction.
The web, in a region of the pole opening which contains no pole
magnet, can also be configured with a different thickness, in order
to enhance the high-speed performance. The ratio described here
refers to the thickness of the web at the edge of the opening and
the thickness of the web at the point of initial contact of a pole
magnet with said web. This ratio in particular results in an
optimum high-speed performance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Forms of embodiment of the invention are described
hereinafter with reference to the attached drawings, wherein
neither the drawings nor the description constitute any limitation
of the invention.
[0035] FIG. 1 shows a partial cross-section though an electrical
machine according to one form of embodiment of the invention.
[0036] FIG. 2 shows a section of FIG. 1.
[0037] FIG. 3 shows diagrams which illustrate the optimization of
the electrical machine represented in FIGS. 1 and 2.
[0038] The figures are schematic only, and are not true to scale.
In the figures, identical reference symbols identify identical
features, or features having the same effect.
DETAILED DESCRIPTION
[0039] FIG. 1 shows a partial cross-section through an electrical
machine 10 with a rotor 12, which is mounted inside a stator 14 for
rotation about an axis. The partial cross-section encompasses one
pole 16 of the rotor 12. The pole 16 is characterized by a V-shaped
pole opening 18, in which two pole magnets 20 are accommodated. The
two pole magnets 20 have a rectangular cross-section, and are
oriented in a V-shape in relation to each other.
[0040] The two pole magnets have a geometrical angular offset wM of
less than 15.degree.. The angular offset wM of the two pole magnets
20 is here the angle through which the two magnets are in each case
rotated in relation to one another such that, in combination, they
constitute a V-shape. In combination, the two pole magnets are
offset by 2*wM.
[0041] FIG. 1 additionally shows the radially outer pole coverage
wA, the radially inner pole coverage wI and the opening coverage
wO, all of which can be expressed as geometrical angles.
[0042] The outer pole coverage wA can be defined by the axial
geometrical angle between radially outer edges 22, that are
circumferentially on the outside, of the pole magnets 20. Ideally,
the outer pole coverage wA lies between 123.5.degree. el and
142.9.degree. el. The angle is expressed in electrical degrees
(.degree. el), thus rendering it independent of the number of poles
16 of the rotor 12. Specifically, an electrical angle w.sub.el is
determined as follows from the geometrical or mechanical angle
w.sub.mech and the pole number p:
w.sub.el=w.sub.mech*p/2
[0043] The inner pole coverage wI can be defined by the axial
geometrical angle between radially inner and circumferentially
outer edges 24 of the pole magnets 20. Ideally, the inner pole
coverage wI lies between 115.7.degree. el and 133.2.degree. el.
[0044] The minimum clearance m between the pole magnets 20, in the
circumferential direction, is ideally less than 3 mm (even where a
central web is present). The pole opening 18 represented in FIG. 1
has no central web. In this case, the clearance m between the pole
magnets 20 can be even smaller than 1.5 mm.
[0045] FIG. 2 shows a section of FIG. 1 in greater detail,
including parameters for the web 28 which separates the pole
opening 18 from an air gap 26, which is arranged between the rotor
12 and the stator 14. A radial thickness hSA of the web 28 between
the pole opening 18 and an outer circumference of the rotor 12 at
the edge of the web 28 or the pole opening 18, in the
circumferential direction, and a radial thickness hSI of the web
28, at the initial point of contact of a pole magnet 20 with the
web 28, are represented. Ideally, the ratio hSA/hSI lies between
0.7 and 1.2.
[0046] With reference to FIG. 1, the stator, in a tooth region 30,
incorporates teeth 32, between which grooves 34 are constituted.
The teeth 32 are secured by a yoke region 36, and the tooth gullet
38 thereof merges into said yoke region 36. At a tooth tip 40,
which lies opposite the tooth gullet 38 and is oriented towards the
rotor 12, the teeth are configured with a T-shape, such that
virtually closed openings through the stator 14 are produced for
the slots 34. The teeth 32, excluding the tooth tip 40, have an
essentially trapezoidal cross-section. The grooves 34 have an
essentially trapezoidal or rectangular cross-section.
[0047] In the grooves 34 a stator winding 42 is arranged, which
comprises three phases 44a, 44b, 44c. In a plug-winding, the
conductors of the stator winding 42 can have been plugged into the
grooves 34 and interconnected at their ends.
[0048] As indicated in FIG. 1, six grooves 34 are assigned to one
pole 16. Given three phases 44a, 44b, 44c, the electrical machine
has a resulting slot number of q=2. Ideally, the electrical machine
has a slot number q greater than or equal to 1.
[0049] In FIG. 1, the following parameters for the stator 14 are
indicated: [0050] the tooth height hz, i.e. the radial distance
from the internal diameter dSI of the stator 14 to the tooth gullet
38, or the radial height or thickness of the tooth region 30,
[0051] the yoke thickness hj, i.e. the radial distance from the
tooth gullet 38 to the external diameter dSA of the stator 14, or
the radial height or thickness of the yoke region 36, [0052] the
tooth width bZA at the tooth gullet 38, i.e. at the radially
outermost position, [0053] the tooth width bZI at the tooth tip 40,
i.e. at the radially innermost position, [0054] the groove width
bNA at the tooth gullet 38, i.e. at the radially outermost
position, [0055] the groove width bNI at the tooth tip 40, i.e. at
the radially innermost position.
[0056] For the stator 14, there are two alternative parameter sets
which, together with the parameters indicated above, are optimum
for the rotor 12:
[0057] Parameter set I: [0058] Ratio hz/hj of the tooth height to
the yoke thickness: 0.959-1.126 [0059] Ratio bZA/bNA of the tooth
width to the groove width at the tooth gullet 38: 1.23-1.35 [0060]
Ratio bZI/bNI of the tooth width to the groove width at the tooth
tip 40: 1.03-1.14 [0061] Ratio hNA/hNI of the groove widths at the
tooth gullet 38 and at the tooth tip 40: 0.9-1.1
[0062] Parameter set II: [0063] Ratio hz/hj of the tooth height to
the yoke thickness: 1.395-1.6376 [0064] Ratio bZA/bNA of the tooth
width to the groove width at the tooth gullet 38: 1.33-1.47 [0065]
Ratio bZI/bNI of the tooth width to the groove width at the tooth
tip 40: 1.06-1.19 [0066] Ratio hNA/hNI of the groove widths at the
tooth gullet 38 and at the tooth tip 40: 0.9-1.1
[0067] The parameters can be achieved, for example, with an
external diameter of the stator dSA between 110 mm and 500 mm.
[0068] The ratio dSI/dSA of the internal diameter dSI to the
external diameter dSA of the stator can ideally range between 0.75
and 0.85.
[0069] Moreover, an optimum ratio d/dSI of the thickness of the air
gap d to the internal diameter dSI of the stator 14 of between
0.0025 and 0.0055 has emerged.
[0070] FIG. 3 shows the results of a multi-objective optimization,
which results in the above-mentioned parameter combinations. FIG. 3
includes diagrams in which two target values for the electrical
machine 10 are represented in each case. It is significant that the
above-mentioned geometrical parameters define the electrical
machine whereas, in multi-objective optimization, optimization
parameters are optimized, which are influenced by geometrical
parameters.
[0071] Each multidimensional point defined by the two optimization
parameters in the diagrams can thus be considered as a dedicated
design point of an electrical machine. By means of a recursive
optimization algorithm, starting from one point, further optimum
points are then identified. All the points considered by the
algorithm are plotted in the diagrams as outlined areas.
[0072] The arrow in each of the diagrams indicates where the
optimum design point would be located, with respect to the two
optimization parameters which are plotted in the diagram. However,
this point cannot be achieved in the event of mutually conflicting
individual objectives. Only a relative optimum for all the
optimization objectives can be determined. The points in the shaded
areas represent sets of optimization parameters, in which all
optimization parameters assume their most optimum form. From these
optimum optimization parameters, intervals for the above-mentioned
geometrical parameters for the electrical machine 10 were then
derived.
[0073] The following optimization parameters are represented, and
have been optimized: [0074] The maximum torque T must be maximized.
[0075] The maximum power P must be maximized. [0076] The
short-circuit current I must be minimized. [0077] The noise level G
must be minimized. [0078] The tonality O must be maximized. [0079]
The cyclic efficiency Z must be maximized. [0080] Material costs K
must be minimized. [0081] Losses V must be minimized. [0082] The
torque ripple R must be minimized.
[0083] The cyclic efficiency Z is significant for hybrid and
electric vehicles, as it has a direct influence upon the range.
[0084] All the parameters indicated are standardized in relation to
a specified maximum value.
[0085] Finally, it should be observed that terms such as "having",
"comprising", etc. do not exclude any further elements or steps,
and terms such as "a" or "one" do not exclude the plural. Reference
symbols in the claims are not to be considered as a limitation.
* * * * *